1. Field of the Invention
The field of the invention relates to method of and apparatus for tenderizing meat, utilizing the enzymatic action of the natural enzymes within the meat, while controlling the surface bacteria by means of intermittent exposure to ultraviolet light.
2. Description of the Prior Art
U.S. Pat. No. 2,650,882 to G. S. Sperti discloses a cyclic process and apparatus for tenderizing meat by subjecting it to irradiation while the meat is maintained at temperatures below 60.degree. F. and preferably well below 45.degree. F. for time intervals sufficient to insure a low surface bacterial count. Sperti notes that:
it is common practice to employ ultraviolet radiation both in pre-chilled chambers and in tenderizing chambers; but inasmuch as intense ultraviolet radiation long continued has a tendency to produce discoloration and sunburn in the meat pieces, it has been the practice to diminish the intensity of the irradiations to a point where discoloration does not occur within the space of time of storage or tenderizing treatments. Under these circumstances, the intensity of the irradiations is not sufficient to control the activity of microorganisms which, under the conditions of temperature well above freezing, and under conditions of moisture hereinafter set forth, multiply rapidly enough to produce sliming, discoloration and odor with a consequently high trimming loss. (Col. 2, lines 25-42) PA1 It has been found that the irradiation of meats at low temperatures is more effective in killing surface microorganisms than at high temperatures, an effect which I believe to be due to the decreased activity and resistance of the microorganisms at low temperatures. Thus, I have found that it is readily possible by treating the surface of meats when the pieces are at low temperatures (comparable to, or only slightly above those of the pre-chill chamber) to use an intensity of ultraviolet light sufficient to produce a high degree of surface sterilization without encountering discoloration. Thus, when the meat pieces have been brought down to temperature in the pre-chill chamber and prior to their removal for tenderizing, I may step up the intensity of irradiation in the prechill chamber for sterilizing***** or I may irradiate the pieces strongly after they have been introduced into the tenderizing chamber but before the temperature has been allowed to rise more than say ten or fifteen degrees above the temperature of the pre-chill chamber. As the temperature of the meat pieces rises, the irradiation is diminished or stopped in order to avoid discoloration.***** Where sterilization is accomplished by ultraviolet radiations, care should be taken with the placement of the light sources or the exposure of the meat pieces to them so as to irradiate all parts of the surface of the meat pieces sufficiently. PA1 The meat is held at the high temperature during a predetermined interval, whereupon the temperature is again lowered to a value at least as low as 60.degree. F. and preferably as low as well below 45.degree. F. Sterilization or some degree of bacteriological control is again practiced at the lower temperature. Where ultraviolet light is employed, the lights are again turned on or increased in intensity. PA1 they are maintained at high temperatures (around 75.degree. F.) for a period of approximately 10 hours after which they are chilled and maintained at a temperature below 45.degree. for a period of approximately 14 hours. The maintenance of meat at relatively low temperatures, but temperatures at which the enzymatic activity can nevertheless occur, following a period of tenderization at quite high temperatures, appears to be an advantage in itself, while as has already been pointed out, the chilling of the meat pieces after a period of high temperature treatment may be required for resterilization, as well as for preventing a too high rise in temperature of the meat adjacent the bone. PA1 beneficial effects of ultraviolet radiation so far as the aging of meat is concerned, are due primarily to the maintenance of the atmosphere of the storage room free from bacteria and not to the direct contact of the ultraviolet rays on the surface of the meat. In other words, ultraviolet radiation retards bacterial propagation in the air and inhibits the growth of the airborne microorganisms, but is of little or no value in controlling the development of bacteria already on the surface of the meat. The wrapper described above, not only screens out the rays which would normally deleteriously affect the red meat and fat but in addition effectively controls the development of bacteria already on the surface of the meat . . . " (Col. 3, lines 1-13). PA1 direct radiation of the cut surfaces of meat results in some darkening. This effect can be minimized by reducing the intensity of direct radiations and securing the sterilization by air circulation. The incidence of energy upon the cut surface of the meat causes a chemical change within the organic compounds of the meat with the incident formation of a protective coagulum having a pigmentation.
In Column 3, lines 13, Sperti states:
Sperti confines the higher intensity radiation to the lower temperature portions of his cycle either using at other times no irradiation at all or only such irradiation as is required to maintain a generally low count of microorganisms in the air of the chamber.
To summarize, this prior art patent teaches that "meat pieces are sterilized by irradiation or otherwise at low temperatures which will be below 60.degree. F. (and preferably well below 45.degree. F. where the meat is irradiated) for time intervals sufficient to insure a low surface bacterial count. Then the ultraviolet light is turned off or dimmed and the temperature of the meat is increased to a higher value, usually between 60.degree. and 90.degree. F."
The humidity of the surrounding air is simultaneously automatically adjusted to values which will ensure substantially no loss of weight by the meat due to evaporation and no condensation on it, not only at the high final temperatures but during the temperature changes aforesaid.
The foregoing cycle is repeated as often as necessary to tenderize the meat to the desired degree.
Sperti states that he has achieved very satisfactory results in tenderizing sides and quarters of beef in treatments in which:
U.S. Pat. No. 2,384,203 to G. Sperti discloses an irradiation process for the treatment of meat during storage and tenderizing wherein the meat to be tenderized is subjected to ultraviolet light only during those periods of time when the meat is at a temperature which does not exceed 45.degree. F.
In this patent Sperti teaches that in order to prevent undue drying and darkening of the meat, it is enclosed in a tight envelope of cellophane, pliofilm, or the like, which is pervious to ultraviolet radiation. The envelope likewise serves to seal the meat against contamination by airborne microorganisms. Means are provided for preventing operation of the ultraviolet lamps whenever the temperature in the storage compartment is above a predetermined 45.degree. F.
Sperti states that the application of relatively brief and relatively high intensity irradiation applied only at lower temperatures, say below 45.degree. F., give better product results both in tenderizing and in storage.
U.S. Pat. No. 2,926,089 to B. E. Williams discloses the method of aging and ripening meat by periodically introducing Thamnidium, a mold strain, into an enclosed space in which sides of beef are housed over a period of 48 hours while the meat temperature is maintained at 70.degree. F. to 75.degree. F. for a period of 32 hours or more after which the meat temperature is reduced to 33.degree. F. to 35.degree. F. Williams periodically sterilizes the atmosphere within the chamber during the cooling period by spraying a compound selected from the group consisting of propylene glycol or tributyl tin oxide into the enclosed space, or wherein sterilization is accomplished during the cooling period by changing the air within the enclosed space by means of electrostatic precipitation.
U.S. Pat. No. 3,377,941 to B. M. Jaremus discloses a domestic refrigerator having a meat aging and tenderizing compartment provided therein in which the meat-tenderizing process as described in U.S. Pat. No. 2,926,089 to B. E. Williams may be practiced on a miniature scale, in a domestic refrigerator, using Thamnidum as an aging "Activator," and subjecting the meat product to ultraviolet rays for the entire 48 hour tenderizing process.
U.S. Pat. No. 2,713,002 to B. E. Williams discloses the method of aging beef by wrapping a freshly killed, skinned carcass in a wrapper which has been soaked in a bactericidal agent. The carcass is housed within the wrapper during the aging process, the wrapper being provided with a plurality of openings to provide a wicking and breathing action which prevents the formation of slime on the carcass. After the wrapped meat has been subjected to an aging process in the presence of ultraviolet radiation it is then transferred to another room where it is chilled while being subjected to additional ultraviolet radiation. This patent states that the:
U.S. Pat. No. 3,300,990 of B. M. Jaremus discloses a thermoelectric meat aging/tenderizing apparatus for fresh meat which in the aging process, when cut, is treated with an aging accelerator, Thamnidum, after which it is placed in a storage zone where the temperature is maintained between 70.degree. F. and 75.degree. F. and a relative humidity above 90% for approximately 48 hours. During the last nine hours of the processing period the meat is continuously exposed to ultraviolet radiation.
Jaremus also describes a tenderizing process wherein fresh meat is maintained between 70.degree. F. and 75.degree. F. for approximately 48 hours while a source of ultraviolet radiation is maintained in continuous operation throughout the entire tenderizing period.
U.S. Pat. No. 2,169,081 to R. F. James discloses a process for ripening and storage of meat by subjecting same to temperatures above 45.degree. F. until internal tenderization has occurred while simultaneously inhibiting surface deterioration by irradiating the meat with ultraviolet light in the range between 2500 and 3000 A.U. during the entire "ripening" and storage periods.
The James patent states that:
U.S. Pat. No. 2,192,348 to R. F. James discloses the use of ultraviolet rays for sterilizing the air which is introduced into a compartment in which meat is to be tenderized. In one embodiment, means are provided for effecting the direct irradiation of all outer surfaces of the meat to action of ultraviolet rays, during the entire two or three weeks tenderization process.
U.S. Pat. No. 2,489,918 to L. J. Menges discloses a process for tenderizing meat, and in particular beef, by placing the meat in a confined area the temperature of which is maintained at 56.degree. F., with a relative humidity of 80% to 85% and wherein air under a velocity of 50-75' per. min. is circulated around the meat wherein the aforesaid conditions are maintained for a period of about 48 hours during which ultraviolet radiations are provided via one 30" generator for every 20 (twenty) square feet of floor space.
U.S. Pat. No. 2,482,507 to Rentschler discloses a method of destroying microorganisms and, in particular, to a method of sterilizing a fluid host by irradiating the host with bactericidal ultraviolet energy.
U.S. Pat. No. 2,906,104 to H. W. Schaefer discloses apparatus for irradiating the contents of a refrigerated cabinet, utilizing ultraviolet rays which are interrupted by means of a motor-driven rotating shield, said shield producing controlled period of irradiation of substantially equal intensity on successive portions of the refrigerator.
U.S. Pat. No. 2,192,348 to R. F. James discloses apparatus for the treatment and storage of food, including meat products, which are housed within a refrigerated case, wherein ultraviolet rays are continuously generated for inhibiting the growth of bacteria and molds on the surface of meats stored in the refrigerated compartment.
U.S. Pat. No. 2,932,573 to W. C. Reiman, a coinventor of the subject invention, discloses a method for treating meat whereby to accelerate the enzymatic activity within the meat product, by irradiating the meat with ultraviolet radiations.
Reiman teaches the continuous irradiation of the surface of meat with ultraviolet rays during the entire meat-treating period.
From the foregoing it will be noted that ultraviolet rays have been extensively used over the past 36 years for the purpose of inhibiting bacterial growth in meat undergoing tenderization by reason of enzymatic action, wherein the meat has been either continuously subjected to the action of ultraviolet rays, during the entire enzymatic action tenderizing process--or wherein the meat products have been subjected to ultraviolet rays, only during those periods of time when the meat is at a temperature of 45.degree. F. or below.
The prior art, as presently known to applicants, is devoid of any teaching which would lead one skilled in the art to arrive at and practice the unique method described in the subject application.